High Flux of Small Sulfate Aerosols During the 1970s Reconstructed From the SE-Dome Ice Core in Greenland

Aerosols significantly affect Earth's radiation budget, thus influencing global climate. In the Arctic, sulfate aerosols are thought to have reduced the warming during the twentieth century. However, trends in past sulfate aerosols are poorly known, especially the aerosol sizes and compositions. Here, we analyze a high-resolution ice core from southeastern Greenland, comparing the seasonal deposition flux of large sulfate salt particles and small sulfur compounds, including non-neutralized sulfuric acid, between the anthropogenic sulfate maximum (1973-1975) and after sulfur emissions control (2010-2012). Between these periods, we find that the large-diameter (>0.4 mu m) flux remains roughly unchanged, yet the small-diameter (<0.4 mu m) aerosol flux significantly decreases. The results indicate that small sulfates were efficiently activated as cloud condensation nuclei during the 1970s, and thus likely increased cloud albedo, offsetting the warming.